RESOLVCONF

NAME

SYNOPSIS

DESCRIPTION

Overwrite (-a) or delete (-d) the nameserver information
record for network interface INTERFACE
and run the update scripts in /etc/resolvconf/update.d/
if the nameserver information has changed.

With -u, just run the update scripts.

PUBLICATION

Normally
resolvconf
is run only by hook scripts attached to network interface configurers
such as
pppd(8)
(for ppp interfaces),
to DHCP clients such as
dhclient(8),
to
ifup(8)
and
ifdown,
and
to DNS caches such as
dnsmasq(8)
(for the loopback interface).
These hook scripts furnish
resolvconf
with information about nameservers.
For example,
dhclient
receives one or more nameserver addresses
during its negotiation with the DHCP server;
its hook script
/etc/dhcp3/dhclient-enter-hooks.d/resolvconf
publishes this information to
resolvconf.

The
ifup(8)
program can be used to configure network interfaces
according to settings in
/etc/network/interfaces(5).
To make
ifup
publish nameserver information to
resolvconf
when it configures an interface, add
dns-
lines to the relevant
iface
stanza in /etc/network/interfaces.
To add nameserver addresses add a line beginning with
dns-nameservers.

dns-nameservers 11.22.33.44 55.66.77.88

Note that one or more addresses can be given,
and note the `s' at the end of the option name.
(Contrast with the
resolv.conf(5)
option
nameserver.)
For each other valid
resolv.conf(5)
configuration option,
you can include, in the stanza,
one line beginning with that option name with a
dns-
prefix.
The resulting stanza might look like the following example.

See the resolvconf package's README file for more detailed information.
For more information about the dns-* options, e.g.,
dns-search,
see
resolv.conf(5).

The administrator can run
resolvconf
from the command line to add or delete nameserver information,
but this is not normally necessary.

SUBSCRIPTION

Nameserver information provided to
resolvconf
is stored for use by subscribers to resolvconf's notification service.
Subscribers that need to know when nameserver information has changed
should install a script in /etc/resolvconf/update.d/
(... or in /etc/resolvconf/update-libc.d/: see below).
For example, DNS caches such as
dnsmasq(8)
and
pdnsd(8)
subscribe to the notification service so that they know
whither to forward queries.

The most important piece of
software that subscribes to the notification service is the set of functions
that make up the GNU C Library
resolver(3).
When nameserver information is updated the script
/etc/resolvconf/update.d/libc writes a new resolver configuration
file to /etc/resolvconf/run/resolv.conf and then runs the scripts in
/etc/resolvconf/update-libc.d/.
To make the resolver use the dynamically generated resolver configuration
file the administrator should ensure that /etc/resolv.conf is a symbolic
link to /etc/resolvconf/run/resolv.conf.
This link is never modified by /sbin/resolvconf.
If you find that /etc/resolv.conf is not being updated,
check to see that the link is intact.

The GNU C Library resolver library isn't the only resolver library available.
However, any resolver library that reads /etc/resolv.conf
(and most of them do, in order to be compatible with the GNU C Library resolver)
should work with
resolvconf.

Subscribers that need to know only when the resolver configuration file
has changed should install a script in /etc/resolvconf/update-libc.d/
rather than in /etc/resolvconf/update.d/.
This is important for synchronization purposes:
scripts in update-libc.d/ are run after resolv.conf has been updated;
the same is not necessarily true of scripts in update.d/.
Examples of packages that do this are
fetchmail(1)
and
squid(8).

Client hook scripts will find the files containing nameserver
information in the current directory.

OPTIONS

-aINTERFACE

Add or overwrite the record for network interface INTERFACE.
When this option is used the information must be provided to
resolvconf
on its standard input in the format of the
resolv.conf(5)
file.
Each line in the file must be terminated by a newline.

-dINTERFACE

Delete the record for network interface INTERFACE.

The INTERFACE name may not contain spaces, slashes or
initial dots, hyphens or tildes.

Following the addition or deletion of the record, resolvconf runs
the update scripts as described in the CLIENTS section.

-u

Just run the update scripts.

ENVIRONMENT VARIABLES

The following variables can be set in /etc/default/resolvconf.

REPORT_ABSENT_SYMLINK

If set to "yes" then
resolvconf
will print a message when /etc/resolv.conf is not a symbolic link
to the
resolvconf-generated
resolv.conf file.
Set to "no" to prevent the printing of this message.
The default is "yes".

TRUNCATE_NAMESERVER_LIST_AFTER_127

If set to "yes" then the update.d/libc script will include
no more nameserver addresses after the first address
that starts with "127."
This is usually the preferable behavior
if the nameserver at 127.* is a local caching nameserver
since it inhibits unnecessary changes to resolv.conf.
When an interface is brought up the local caching nameserver
is informed by
resolvconf
of any new nameserver addresses
and the additional name service is made available to applications
that make use of the resolver and the local caching nameserver;
the applications themselves do not need to be notified of the change.
A disadvantage of this mode of operation is that applications have
no secondary or tertiary nameserver address to fall back on should
the local caching nameserver crash.
Insofar as a local nameserver crash can be regarded
as an unlikely event,
this is a relatively minor disadvantage.
Set to "no" to disable this truncation feature.
The default is "yes".

NAMED_RUN_DIR

This is the directory where the dynamically generated
named.options
file will be placed. See the README file for more information.
The default location is
/var/run/bind/.

FILES

/etc/default/resolvconf

See the ENVIRONMENT VARIABLES section.

/etc/resolvconf/run

This is either a directory where nameserver information can be stored
or a symbolic link to such a directory.
Clients should not make any assumptions about the canonical location
of this directory or the hierarchy that is constructed under it.

/etc/resolvconf/interface-order

Determines the order in which nameserver information records are processed.
See
interface-order(5).

/etc/resolvconf/resolv.conf.d/base

File containing basic resolver information.
The lines in this file are included in the resolver configuration file
even when no interfaces are configured.

/etc/resolvconf/resolv.conf.d/head

File to be prepended to the dynamically generated resolver configuration file.
Normally this is just a comment line.

/etc/resolvconf/resolv.conf.d/tail

File to be appended to the dynamically generated resolver configuration file.
To append nothing, make this an empty file.
This file is a good place to put a resolver
options
line if one is needed, e.g.,

options inet6

BUGS

Currently
resolvconf
does not check the sanity of the information provided to it.